Warning: Beach closures may not be valid

Nothing will ruin a day at the beach like a sign in the sand
that reads, "Warning: Contaminated Water. Unsafe for Swimming or
Contact."

According to the Natural Resources Defense Council, there were
more than 13,000 closures and advisories at ocean and freshwater
beaches in the United States in 2001 -- the vast majority prompted
by lab tests showing elevated levels of fecal bacteria in the
water.

But
a recent study in the journal Environmental Science &
Technology (ES&T) is raising questions about the
reliability of water monitoring programs now in use at most U.S.
beaches. The study also has uncovered a surprisingly strong
correlation between beach pollution and the forces of nature --
including rainfall, sunlight and the gravitational pull of the
moon.

Alexandria
Boehm, the Clare Boothe Luce Assistant Professor of Civil and
Environmental Engineering, collects a sample of ocean water at
Capitola Beach to be tested for bacterial contamination.Photo: L.A. Cicero

"There are many factors that can influence the concentration
of bacteria in a sample of water," said Alexandria B. Boehm, the
Clare Boothe Luce Assistant Professor of Civil and Environmental
Engineering at Stanford and lead author of the ES&T
study. After conducting extensive field studies of Southern
California beaches, Boehm is extending her research to the sandy
shores of Northern California not far from the Stanford
campus.

"A
lot of water sampling is done once a day, but there usually is a
one- to four-day delay between the time a sample is taken and
testing results are known," she explained. "In our study, we found
that a lot of pollution events last just one day or one hour, so
the problem is likely to have passed by the time a warning sign is
posted."

The
result, Boehm said, is that people may be barred from swimming at
beaches that are actually clean, while contaminated beaches may be
inadvertently kept open, exposing swimmers, snorkelers and surfers
to a wide range of illnesses -- some producing mild symptoms (such
as chills, fevers and upset stomachs) and some that are potentially
lethal (including hepatitis and meningitis). Beach closures also
can have a serious economic impact on restaurants, shops and other
local businesses.

"Decisions to post or close a beach should not be based on the
concentration of indicator bacteria in a single grab sample," Boehm
noted. "It's not that the single sample standard doesn't protect
people, it also overprotects them and says the beaches are dirty
when they're not."

Surfing and science

An
avid surfer, Boehm traces her interest in coastal ecology to her
childhood in Hawaii. "I love being in the ocean," she said. "I grew
up in Oahu, so I grew up swimming, surfing, playing in the water
and diving."

After graduating from high school, Boehm moved to Southern
California, where she earned an undergraduate degree at Caltech and
a doctorate in environmental engineering at the University of
California-Irvine. Much of her free time was spent at nearby
Huntington Beach, one of Orange County's most popular surfing
spots. In the summer of 1999, while Boehm was completing her
doctoral thesis, Huntington Beach was thrown into the national
spotlight when Orange County officials shut down several miles of
beachfront after tests revealed high concentrations of fecal
bacteria.

"The public was outraged and demanded that someone be blamed
for the dirty water," Boehm recalled, "but to this day, no one has
determined the source of the contamination."

More than a million people visit Huntington Beach in a typical
summer, so the local economy was devastated by the closure, which
lasted more than two months. When she joined the UC-Irvine faculty
in 2000, Boehm decided it was a perfect time to conduct an in-depth
study of the water quality at Huntington Beach.

"One of my favorite spots to surf was right at the mouth of
the Santa Ana River, where bacteria concentrations are typically
high," Boehm said. "It was kind of nice just being in the place
where I was spending so much time studying and doing
research."

With the help of the sanitation district and other local
agencies, Boehm and her colleagues analyzed more than 100,000 water
samples that had been collected at 17 monitoring stations along the
beach since 1958.

"We
found that water quality at Huntington Beach today is no worse than
it was in the '80s," she noted. "In fact, it's actually getting
better."

The
study showed that pollution levels dramatically declined following
the construction of a 4.5-mile-long sewage outfall pipe in 1971.
Many of the beach closures that have occurred since than can be
attributed to tougher state water quality standards, Boehm
said.

"We're becoming more conservative about what is safe and what
is not safe," she added. "I think that the rash of beach closures
that have been occurring recently here and throughout the United
States are because of changes in the way that people monitor and
the fact that regulations have become more strict."

Rain, tides and sunlight

Nature also plays an important role in determining beach
quality. The ES&T study revealed that, on average,
bacterial levels at Huntington Beach were three times higher in the
rainy months of January, February and March than during the dry
summer months of June, July and August when beach use is at its
peak. The apparent cause of this seasonal disparity is sewer system
failures and stormwater runoff that occur during heavy winter
rains.

More surprising was the discovery of a direct relationship
between beach contamination and the lunar cycle. Tides on Earth are
determined by the gravitational pull of the moon, and the range
between high and low tides is greatest during full and new moons.
At the other extreme, tidal range is minimal during neap tides,
which occur in the first and third quarters of the moon.

"In
our study, we found that, at certain locations, water quality was
worse during full and new moons than during neap tides," Boehm
explained. "I'm currently trying to see if there is some
oceanographic pattern that can account for it. Perhaps polluted
ground water is pumped into the surf zone during full and new moons
when the tide range is bigger."

In
their study, Boehm and her co-workers analyzed data collected
during two intensive sampling surveys at Huntington Beach. In one
survey, water samples were collected every hour for two consecutive
weeks. In the other survey, researchers spent a night at the beach
collecting samples every 10 minutes.

"One of the things we found during these short-term studies
was that water quality varies over the course of the day," she
said. "That's because sunlight influences the concentration of
bacteria in the water, so if someone goes out and collects a sample
in the morning, bacteria levels will be much higher than if they
collect the sample at noon or at 2 p.m."

Because fecal bacteria are so sensitive to sunlight, Boehm
recommended that authorities consider the time of day a sample of
water is taken when assessing human health risk. "Right now,
there's no time-of-day associated with the standards set in place
by the government," she observed.

In
the ES&T study, Boehm and her colleagues also suggested
replacing single sample monitoring with a more reliable method
known as geometric mean sampling. "The geometric mean standard is
much better because it integrates water quality from the last 30
days into the measure of how clean the water is," she said, adding
that it gives authorities a more accurate standard for making
decisions about beach postings and closures.

Northern California

This past summer, Boehm left UC-Irvine and moved 500 miles
north to join the Civil and Environmental Engineering Department at
Stanford. Upon her arrival, she received a Clare Boothe Luce
Professorship -- an award given by the Henry Luce Foundation to
promote the advancement of young American women in the sciences,
engineering and mathematics.

Included in the endowment is a two-year stipend that will
allow Boehm to extend her research to the beaches of Northern
California, including Santa Cruz County -- a popular surfing and
sunbathing spot located on Monterey Bay about 50 miles southwest of
Stanford. Like Huntington Beach, Santa Cruz beaches are popular but
have suffered many closures and advisories in recent
years.

"I
want to see if I find any of the same results in Santa Cruz that I
found at Huntington Beach," Boehm said. "I want to see if there are
the same seasonal patterns in the water quality, and if there is
variability during the day."

She
also plans to continue her research on lunar patterns to see if
they can be used as a regulatory tool to predict pollution events.
"If you know that water quality is worse during full and new moons,
then maybe you should just shut the beach during that time instead
of continually monitoring it," she explained.

"The best thing you can do to make beaches cleaner is to be
aware of what's going on in your community and tell the officials
in your county that you are concerned about beach water quality.
Also, don't put things down the storm drain that you wouldn't want
to swim in."

Although ocean water at Santa Cruz is much cooler than at
Huntington Beach or Hawaii, Boehm predicts that it won't be long
before she dons her wetsuit and rides the wild surf: "I'd like to
get out and do field work with my students, including
undergraduates. It sounds like fun -- camping on the beach, surfing
and sampling water!"

Other co-authors of the ES&T study were Stanley B.
Grant and Joon H. Kim of UC-Irvine; Samuel L. Mowbray and Charles
D. McGee of the Orange County Sanitation District (OCSD); and
Catherine D. Clark, Denise M. Foley and Daniel E. Wellman of
Chapman University. The study was supported by the National Water
Research Institute, OCSD, the Santa Ana Regional Water Quality
Control Board and five Southern California cities including
Huntington Beach.